A transparent electrode for use in solar cells, displays, touch screens, and so on is an electrode formed by depositing a conductive metal thin film on a transparent film or glass substrate so as to be transparent and electrically conductive.
Among transparent electrodes, an ITO electrode is mainly used and it is formed by depositing an indium tin oxide thin film on a transparent substrate. ITO has disadvantages of high manufacturing cost due to high prices of indium and of poor durability and flexibility due to chemical instability.
In order to solve these problems, i.e., to replace ITO electrodes, alternative transparent electrodes made of various different materials and having various structures have been studied and developed to have excellent durability and flexibility.
Transparent electrodes that have been developed so far are electrodes formed by depositing a metal thin film using silver, platinum, gold, copper, and the like or a combination thereof instead of indium, on a transparent substrate.
Among conventional transparent electrodes, a transparent electrode made of polycrystalline copper has an advantage of low manufacturing cost due to the low price of copper. However, it has disadvantages of structural defects and nonuniform grains attributed to the polycrystalline structure. Therefore, with the use of polycrystalline copper, it was impossible to form a thin film with a nano-sized line width. Furthermore, polycrystalline copper cannot be applied to flexible devices due to low mechanical stability and flexibility, which increase sheet resistance when the sheet is being bent.